Process for heat transmission



Pa'tented July 2, 1935 fUNlTED STATES 2,006,411 PROCESS FOR HEAT TRANSMISSION Ludwig Rosenstein, San Francisco, Calif., as-

signor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application July 31, 1933, Serial 15 Claims. (01. 252

The present invention is concerned with heating fluids for high temperature work such as used for indirect heating, power cycles and the like.

This method is useful in the art of distillation 5 or evaporation of liquids and is particularly apsolidify at relatively low temperatures.

plicable when the distillation or evaporation is to be carried out at high temperatures and under subatmospheric pressure. It finds specific usage in the distillation of mineral oils for the manufacture of lubricants. I

The present invention provides for the utiliza tion of a class of compounds as heat transmitting material which are generally able to resist high temperatures without decomposing, and which can be used at ordinary or slightly raised pressures, which makes it possible to use simplified apparatus.

The substances as a class are compounds of relatively low volatility and of comparatively high boiling point as well as inert and stable.

When the operating temperature is above that at which the heating agent is fairly stable, it may be desirable to stabilize the agent or agents by incorporating with it or them a substance capable of overcoming any decomposition tendency, preferably a substance-of higher boiling temperature which will by mass action or otherwise restrict or obviate any decomposition reaction, especially during prolonged heating.

- The heat transfer medium may be compounded with certainsubstances to modify its tendency to Sub- stances as p-hydroxy diphenyl, pyrene, and naphthane or their mixtures are useful. Besides the modifying agents, the heat transfer medium may have incorporated therewith one or more stabilizing substances as described heretofore.

My. heat transfer medium, which may or may not have one or more" of the above-mentioned auxiliary agents incorporated therewith, may, if desired, be employed in conjunction with one or more of the conventional heat transfer mediums as diphenyl, diphenyl oxide, diphenyl methane, I (ii-diphenyl oxides or ethers, and the like.

My invention comprises the utilization as heat transfer medium, of secondary alkyl esters of polycarboxylic acids which acids may be of allphatic, aromatic or aralkyl character and may or may not be further substituted. Unsaturated as well as saturated polycarboxylic acids may be used and they may be either di-, .tri-, tetracaris present at least one secondary alkyl radical. I include also the symmetrical neutral esters as well as asymmetrical esters which contain different secondary alkyl radicals on the carboxyl groups. a

As illustrative of the various compounds which may be utilized due to their high-boiling temperatures, may be mentioned the isopropyl, secondary butyl, secondary amyl, secondary hexyl, and higher secondary alkyl esters of phthalic acid, terephthalic acid, methyl-phthalic acid, isophthalic acid, citric acid, maleic acid, malic acid,

tartaric acid, succinic acid, phenyl-succinic acid, trimesicacid, pimelic acid, glutaric acid, methyl malonic acid, malonic acid benzyl-malonic acid, sebacic acid, pyromucic acid, itaconic acid, aco- 'nitic acid, fumaric acid, and the like, as well as their homologues, analogues and substitution products.

Particularly suitable are the neutral esters as the diisopropyl, secondary dibutyl, secondary diamyl, secondary dihexyl phthalates and their homologues as well as those of a mixed character as secondary butyl methyl phthalate, secondary amyl ethyl phthalate, secondary butyl ethyl phthalate, isopropyl methyl phthalate, isopropyl secondary butyl phthalate.

While I have in the foregoing described in some detail the preferred embodiment of my invention and some variants thereof, it will be understood that this is only for the purpose of making the invention more clear and that the invention is not to be regarded as limited to the details of operation described, nor is .it dependent upon the soundness or accuracy of the theories which I have advanced as to the advantageous results attained. On the other hand, the'invention is to be regarded as limited only by the terms of the claims, in which it is my intention to claim all novelty inherent therein as broadly as is possible in view of the prior art.

I claim as my invention:

1. In a process for transmitting heat to fluids in indirect contact with heat transmitting material, the step of employing a secondary alkyl ester of a polycarboxylic acid of relatively highboiling temperature as the heat transmitting ma terial.

2. In a process for transmitting heat to fluids in indirect contact with heat transmitting material, the step of employing a secondary alkyl ester of an aromatic polycarboxylic acid as the heat transmitting material.

3. In a process for transmitting heat to fluids in indirect contact with heat transmitting maester of an aromatic polycarboxylic acid as the heat transmitting material.

4. In a process for transmitting heat to fluids in indirect contact with heat transmitting material, the step of employing a secondary polybutyl ester of an aromatic polycarboxylic acid as the heat transmitting material.

5. In a process for transmitting heat to fluids in indirect contact with heat transmitting material, the step of employing a secondary polyamyl ester of an aromatic polycarboxylic acid as the heat transmitting material.

6. In a process for transmitting heat to fluids in indirect contact with heat transmitting material, the step of employing a secondary alkyl ester of a dicarboxylic acid of relatively highboiling temperature as the heat transmitting material.

7. In a process for transmitting heat to fluids in indirect contact with heat transmitting material, the step of employing an isopropyl ester of phthalic acid as the heat transmitting material.

8. In a process for transmitting heat to fluids in indirect contact with heat transmitting material, the step of employing a secondary -hutyl ester of aphthalic acid as the heat transmitting material.

9. In a process for transmitting heat to fluids in indirect contact with heat transmittingmaterial, the step of employing a secondary alkyl ester or a phthalic acid as the heat transmitting. material.

' terial, the step of employing a poly-isopropyl 10. In a process for transmitting heat to fluids in indirect contact with heat transmitting material, the step of employing a secondary dialkyl ester of a phthalic acid as the heat transmitting material.

11. In a process for transmitting heat to fluids in indirect contact with heat transmitting material, the step of employing a diisopropyl phthalate as the heat transmitting material.

12. In a process'for transmitting heat to fluids in indirect contact with heat transmitting material, the step of employing a secondary dibutyl phthalate as the heat transmitting material.

13. In a process for transmitting heat to fluids in indirect contact with heat transmitting material, the step of employing a secondary diamyl phthalate as the heat transmitting material.

14. In a process for transmitting heat to fluids in indirect contact with heat transmitting material, the step of employing a secondary alkyl ester of a polycarboxylic acid of relatively highboiling temperature as the heat transmitting material, in conjunction with a stabilizing agent which is efiective at relatively high temperatures to stabilize the heat transmitting material against decomposition.

15. In a process for transmitting heat to fluids in indirect contact with heat transmitting material, the step of employing a secondary alkyl ester of a polycarboxylic acid of relatively highboiling temperature as the heat transmitting material, in conjunction with a modifying compound which reduces its solidifying temperature.

LUDWIG' ROSENSTEIN. 

